@noisesmith Do you know why instrument of function foo causes a function arg of foo to be called additional times with arguments that the intrumented call is not itself calling? I can understand doing that if you were doing generative testing on foo, but don't see the rationale for why one would want to do that for instrument.

My understanding is that's the only way spec has to validate a function argument

Makes sense. 20 times may be more than needed for that purpose, but probably tunable.